Plan and commit? Its a vacation not a prison sentence. Make reservations if you want but know that well over 50% of time slots are held for booking on board. Even as late of the day you want special dining you can get in you may just have to wait a bit.
Whether it is worth it or not depends on your point of view. I find that we use it two or three times on a typical cruise so we have decided that it is not worth the money,
NCL is just telling you to stay on top of requirements. it has always been the passengers responsibility regarding visas and they are just letting you know that you need to be alert for any special health requirements so that you don't show up for boarding and get denied. Letter is nothing to be concerned about.